Machines which automatically pit a drupe have laid the foundation for an agribusiness which makes it possible for a person with even less than average income to enjoy fruits and vegetables which would otherwise be consumed only by the wealthy. Such machines are the subject of U.S. Pat. Nos. 2,157,518; 2,219,832; 2,630,205; and 2,688,352 to Ashlock, Jr.; of U.S. Pat. Nos. 3,153,473; and 3,556,281 to Margaroli et al.; and of U.S. Pat. Nos. 4,090,439 and 5,577,439 to Chall et al. and Cimperman et al., inter alia. Such machines have successfully achieved in the U.S. what is still done manually in countries where human labor is relatively inexpensive.
In the aforementioned pitting machines, a pitting knife or an assembly of plural pitting knives in a pitting head, cuts through the skin and flesh of the drupe being pitted, ejects the stone, and is then retracted leaving a substantially central passage in the drupe.
When a moth chooses a drupe to nurture its progeny, it lays its eggs on or near the drupe, typically on its upper surface. The eggs progress to the larva stage. The time it takes an egg to get to the larva stage typically corresponds uncannily to the period during which the drupe ripens. As the drupe ripens, a portion of its skin immediately surrounding its stem, tends to pull away from the stem and at some stage, may do so, leaving a narrow passage through which a larva burrows its way into the flesh of the ripe drupe. The larva feeds on the ripe flesh of the drupe, and as the larva matures, its excretions, referred to as "frass", build up within the now contaminated drupe. When the contaminated drupe is harvested and pitted, the frass, if not the larva itself, is left behind in the passage within the pitted drupe because a pitting knife cannot remove the frass even if it successfully ejects the larva with the pit.
United States Standards for Grades of Dates specifies a defect when an unacceptable percentage of dates are "affected by insect infestation--presence of dead insects, insect parts, or excreta "frass" (no live insects are permitted)."
A typical harvest may include from relatively few, to an economically disastrous percentage of contaminated fruit, and the extent of contamination can only be estimated by inspecting a large number of individual fruits. To date, when contamination is extensive, contaminated fruit has been disposed of as garbage, because there is no economical method of decontaminating the fruit. Worse, since it is currently impractical to sort contaminated fruit from uncontaminated fruit, marketable fruit is discarded along with the contaminated fruit.
When contamination is not extensive, the problem of removing the contaminants from within a pitted drupe has been addressed, unsuccessfully for the most part, by soaking the fruit in water, or passing the pitted fruit under a cascading stream of water, with the faint expectation that some of the water will enter the pit-free passage and flush away the frass. Besides being only marginally effective, both methods result in dissolving or otherwise sacrificing an unacceptably large portion of a fruit, such as a date or a prune, which typically has a relatively high water-soluble sugar content.
A pitting knife is usually made from hard stainless steel. Typically, plural pitting knives are mounted in a knife assembly held within the confines of a pitting head which houses the driving mechanism for timing and thrusting the knives into rows of fruit individually held in chucks, which are in turn, mounted on carriers carried by a conveyor belt. One does not expect to use a pitting knife for any purpose other than its designated purpose. One does not consider boring a pitting knife. Nevertheless, this invention does so; and thereby provides for contacting the S walls of the passage of a pitted drupe with a decontaminating quantity of a decontaminant fluid, thus providing an effective solution to the problem of drupes internally contaminated with contaminants such as "frass".